The invention relates generally to gasifier additives and, more particularly, to gasifier additives for reducing slag penetration into a refractory lining of a gasifier.
Coal and other hydrocarbons may be subjected to partial combustion to produce gases, e.g., CO and H2, that are useful as fuels and starting materials for chemical syntheses. This gasification typically takes place in large furnaces that allow the hydrocarbon to be partially burned at high temperatures to produce the desired gaseous products of the reaction. In addition to the desired products, the by-products of the reaction may include waste products, such as slag. Slag is a blend of inorganic oxides, initially present as minerals within the hydrocarbon feed, that is produced as a viscous liquid by-product in a slagging gasifier when the coal, coke, or other hydrocarbon is partially oxidized. The slag may, for example, contain silica, aluminum oxide, calcium oxide, iron oxide, magnesium oxide, and other inorganic oxides.
To contain the heat of the reaction, the walls of the gasifier may be lined with a refractory material that is able to withstand high temperatures. Typically, the refractory material is porous. For example, common refractory materials are sintered bricks with highly connected pore structures. These materials are vulnerable to damage by the slag byproduct of the gasification reaction. As the liquid slag byproduct flows along the walls of the gasifier, it infiltrates into the pores in the refractory material. This infiltration may cause degradation of the refractory material through cracking/spalling, grain separation, and/or dissolution.
As a result of slag infiltration, the refractory material that lines a gasifier may degrade relatively quickly and may need to be replaced several times during the life span of the gasifier. The refractory material may be replaced by workers entering the gasifier and removing the damaged bricks or, in certain cases, the entire lining. Because the gasifiers are operated at very high temperatures, this involves shutting the gasifier down and allowing it to cool for several days until workers can safely enter. Such replacement of the refractory material is generally costly, both in terms of the materials and labor involved and operating time lost, because the gasifier cannot run for days to weeks during the replacement process.